a. Field of the Invention
This invention relates to a fall arrest block for use by a workman working above the ground. The block will be connected to a secure fixed point, and a lifeline wound on the block is connected to a harness worn by the workman, with the lifeline winding up and unwinding under spring control whilst the workman moves around, but locking up and providing a soft landing if the workman falls.
b. Related Art
In the event of a fall, fall arrest blocks conventionally work by switching in a friction brake which slows down the rate at which the lifeline is unwound from a drum, whilst absorbing energy in doing so.
One prior art fall arrest block is disclosed in US patent document 2005/269153 A1. This discloses a fall arrest block that uses a section of lifeline formed from two lengths of line sewn together. If a worker falls, the fall is broken by the ripping apart of these two lengths, which helps to dissipate energy.
One concern with this arrangement is that if the fall is severe enough, the full length of the sewn sections will be torn apart. Although there is a fixed length lifeline in parallel with the torn sections having a length longer than that of the sewn sections when torn apart, a problem arises in that the energy absorbing function ceases as the two sewn sections become fully separated. This document therefore proposes the use of a third section in parallel in the form of an elastic section. This adds to the complexity and bulk of the fall arrest block.
It is therefore an objection of the invention provide a fall arrest block that is compact, both in terms of the lifeline spooling mechanism, as well as with the energy absorbing feature used to controllably arrest the fall of a worker secured to the fall arrest block.